A new technology, the organic light emitting diodes (OLEDs) is revolutionizing the display industry that has been dominated for the past three decades by liquid-crystal displays (LCDs). The LCD is an electronically modulated optical device shaped into a thin, flat panel made up of any number of color or monochrome pixels filled with liquid crystals (LCs are substances that exhibit a phase of matter that has properties between those of a conventional liquid and those of a solid crystal) arrayed in front of a light source (backlight) or reflector. The OLEDs, that are rapidly replacing the LCDs, are light emitting diodes (LEDs) whose emissive electroluminescent layer is composed of a film of organic compounds. The emissive electroluminescent layer contains a polymer that allows suitable organic compounds to be deposited in rows and columns on a flat carrier by a simple "printing" process resulting in a matrix of pixels that emit light of different colors.
First used in 1999 in car stereos, displays made from OLEDs are now starting to make a real impact in consumer electronics. OLEDs are display devices that enclose a series of organic films between the cathode and anode. They do not require backlighting requiring less power, yet, are emissive. This, therefore, allows smaller and more efficient displays that make them ideal for compact applications, such as cell phone displays, digital camera displays, MP3 displays, and thin large format displays (flat panel TVs). The OLEDs can be used in television screens, computer monitors, advertising boards, in large-area light-emitting elements, and light sources for general space illumination. OLEDs typically emit less light per unit area than inorganic solid-state based LEDs which are often designed for point-light sources. By 2011, OLED material is expected to have a display market opportunity approaching $3 billion worldwide.
Because there is no need for a backlight, an OLED display can be much thinner than an LCD panel. However, the rapid degradation of OLED materials has limited their use so far.
Of particular interest in the display industry is mastering of the quantum dot-based LEDs (QD-LED) technology for the purpose of developing low-cost, efficient, bright, color-saturated, and large-area color displays compatible with flexible substrates. High expectations regarding this type of display result from the superior performance of QD-LEDs in comparison with conventional display devices, such as cathode-ray tubes (CRTs), liquid crystal displays (LCDs), and organic light-emitting-diodes (OLEDs). The advantages of the QD-LED technology include (Table 1) the development of low-cost, solution-based processing of high performance LEDs out of mono-dispersed and well-characterized quantum dots. This is driven by the need to explore the next generation of flexible panel displays featuring high brightness and contrast, a wide viewing angle, rich selection of colors, small depth, low power consumption, and long life times. Several groups have focused their research on the refined synthesis and surface modification of colloidal quantum dots, and have fabricated electroluminescent (EL) devices from thin quantum dot films, exhibiting saturated colors and broad wavelength emission. A number of companies have geared their R&D efforts toward the development of QD-LEDs as an alternative technology for the next-generation flat panel displays. However, QD-LEDs are much less developed in comparison to both conventional inorganic semiconductor LEDs and OLEDs because very few R&D groups possess the expertise in this emerging technology. Furthermore, there are still no commercial suppliers of high quality (electronic grade) nanocrystals required to prove their worth for commercial optoelectronic device applications.
Ocean NanoTech is the pioneer in the synthesis and stabilization of quantum dots for display applications. Through close collaboration with the experts in device fabrication, the performance of Ocean’s QD-LEDs approaches those of the OLEDs. The Figure below shows a quantum dot emission picture of Ocean’s QD-LEDs. More detailed information about the device performance can be found in our recent publication in Nature Photonics, Nano Letters, APL, ACSnano.